Hi again everyone!

I’m trying to implement a simple SketchUp command that draws equidistant parallel lines inside a polygon – all of them perpendicular to a given edge. As an example, if the user selects the trapezoid below and the bottom edge, the following tiling should happen:

This works fine under my current implementation, whose main function I will include later.

However, if I start with something like

my command will only do the following:

As you can see, the tiling isn’t quite complete towards the right of the polygon (and neither it is to the left, but let’s ignore that aspect for now).

Now, if I comment out the line responsible for drawing edges and instead I call `Sketchup.active_model.entities.add_cpoint`

, I do get the correct intersection points:

For brevity, I will only include the main function of my command, but you can assume that there is some logic dealing with line equations, intersections and point containment (hopefully correct!):

```
def tile(face, edge, width)
start_point = edge.start.position
# The face will change as we tile it, so save the original edges (except
# the currently selected one).
other_face_edges = []
face.edges.each do |face_edge|
if face_edge != edge
other_face_edges << face_edge
end
end
edge_line = Line.new(edge)
max_inner_intervals = (edge.length / width).to_i
# Ignore the hardcoded range for now; it will be done properly in the future.
(0..12).each do |n|
new_edge_point = get_point_on_edge(edge, start_point, width, n)
perp_line = edge_line.perpendicular(new_edge_point)
# Needed for n < 0 and n > max_inner_intervals.
intersection_points = []
other_face_edges.each do |face_edge|
intersection_point = perp_line.intersect(Line.new(face_edge))
if is_contained?(intersection_point, face_edge)
# Handle one intersection point first.
if 0 <= n && n <= max_inner_intervals
Sketchup.active_model.entities.add_edges(new_edge_point, intersection_point)
else
intersection_points << intersection_point
# The line adding a point for the bad case (this is used for debugging).
# Sketchup.active_model.entities.add_cpoint(intersection_point)
end
end
end
if intersection_points.length == 2
# The line that is supposed to add an edge between 2 points on the right.
Sketchup.active_model.entities.add_edges(*intersection_points)
end
end
end
```

The problem happens at the very end: the call to `add_edges`

only creates the line when `n = 6`

(I know, the `(0..12)`

should be replaced with something more robust down the road, but this is just development work; `n = 0`

is the leftmost vertical line).

If I comment out this offending line and uncomment the one adding construction points I will end up with the last picture, thus showing that the intersections have been correctly computed. Therefore, I’m not sure what’s causing this behavior (I only have 2 points after all, so the line segment should be drawn without problems).

Thanks for reading and sorry for this rather long message! I would greatly appreciate your help!